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From: kentrox!ktxc5!brent@uunet.uu.net (Brent Capps)
Newsgroups: comp.dcom.telecom
Subject: Re: Supervision / Call Forwarding No Answer
Message-ID: <13049@accuvax.nwu.edu>
Date: 4 Oct 90 19:00:27 GMT
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In article <12985@accuvax.nwu.edu>, kabra437@pallas.athenanet.com (Ken
Abrams) writes:

>>[stuff about call transfer feature encountering a busy signal]

> Are you really sure it works this way?  Is a PBX involved?  The rule
> used to be (and STILL should be) that CFDA (call forwarding-don't
> answer) should only be sent to a number in the SAME SWITCH.  The
> reason for this is the concern you expressed about the confusing
> progress of the call and the posibility of the supervision getting
> fouled up as the call is passed to another switch.

[Moderator states that Ameritech call transfer is not confined to
the same CO, LATA or even area code]

When the CF feature is datafilled for a particular line on a Northern
PBX/Centrex CO (and this probably holds true for AT&T equipment as
well), the craftsperson has the option of blocking the second leg of
the call from being extended along a trunk.  The reason for this has
nothing to do with supervision difficulty.  It has to do with
preventing Joe Blow from forwarding his work phone at SchmuckCo
Industries to Grandma's number in Ulan Bator, then going home and
dialling his work number, causing the call to be forwarded to
Grandma's number while Joe only gets charged for a local call
(SchmuckCo Industries eats the rest of it, because the forwarding
party pays for the second leg).

The same thing goes for the 3WC feature.  Supervision is not 'passed
along' to the next switch; instead the CF software on SchmuckCo
Industries' PBX or Centrex CO determines that it needs to hold the
first leg while originating the second leg to Grandma's number in Ulan
Bator.  When she answers, both legs of the call are condensed onto a
three-port conference bridge.  The PBX or Centrex CO continues to
monitor the connection for billing purposes; when it sees a disconnect
from either party it tears down the call.

By the way, international calls can be selectively blocked by 3WC/CF
as well.


Brent Capps                          uunet:  ...!kentrox!brent
Kentrox Ind., Inc.                   pstn:   (503) 643-1681 x325
Portland, OR                         "insert standard disclaimer here"